Diffusion types

The substrate has to be prepared for cementation. The surface must be clean and free of oxide. Corners and edges are particularly important in diffusion-type coatings sharp edges are usually detrimental. Barrel finishing, ie, tumbling in a barrel with abrasive media, may result in the desired shape. 

Multistage pumps may be of the volute type (Fig. 10-41), with single- or double-suc tion impehers (Fig. 10-42), or of the diffuser type (Fig. 10-43). They may have horizontahy split casings or, for... 

Air jets can be classified according to the diffuser type as follows (Fig. 7.19) ... 

Zone 2 is a transition zone, and its length depends upon the diffuser type. For a compact jet the transition zone typically extends to eight or ten diameters from the outlet. Within this zone, the maximum velocity may vary inversely with the square root of the distance from the outlet. Some researchers 3-5 suggest use of a simplified scheme of the jet (Fig. 7.20b) with a transition cross-section for practical purposes. 

The centerline temperature differential in Zone 3 of the diffuser jet is proportional to the value of the K, coefficient, which, along with the fC, coefficient, depends upon jet and diffuser types and supply conditions. The theoretical value of the K2 coefficient, according to Shepelev, is 2.49. Experimental data reported by Grimitlyn show Ki to be 2.0. 

Characteristic of most equations for surface-controlled kinetics, as opposed to diffusion-controlled kinetics, are a number of partial pressure terms, often to high powers. When large changes in partial pressures are made, differences between the observed and the calculated reaction can easily equal a factor of 1000 or more. When diffusion-type kinetics are used, one seldom finds differences exceeding a factor of two or three. While this may not seem very accurate, comparison of the two methods is rather startling. 

Electrochemical cells have also been proposed for carbon that employ a eutectic molten salt mixture of Li2C03 Na2C03or LiCl-CaCl2-CaC2 as the electrolyte. A diffusion-type meter has also been developed for both small-scale and reactor sodium . 

The time savings and improved spatial resolution of MRI measurements over traditional measurements are profound advantages of MRI. MRI can provide similar information in less than 1 h when literally it would otherwise require days. This would be of particular interest in diffusion type experiments where spatial concentration changes with time are measured. In addition, the same sample can be... 

Small-step rotational diffusion is the model universally used for characterizing the overall molecular reorientation. If the molecule is of spherical symmetry (or approximately this is generally the case for molecules of important size), a single rotational diffusion coefficient is needed and the molecular tumbling is said isotropic. According to this model, correlation functions obey a diffusion type equation and we can write... 

These are Green s functions diffusing in what is interpreted as an imaginary time [3, according to the Bloch equation, dp/8(3 = JYp (a diffusion-type partial differential equation). These Green s functions satisfy the equation... 

Antibodies raised against the Ap peptide were subsequently used to identify more diffuse types of Ap-containing deposits in AD brain by immunohistochemistry. Diffuse Ap peptide deposits lack the... 

The resistance thermometry is based on the temperature dependence of the electric resistance of metals, semiconductors and other resistive materials. This is the most diffused type of low-temperature thermometry sensors are usually commercial low-cost components. At very low temperatures, however, several drawbacks take place such as the low thermal conductivity in the bulk of the resistance and at the contact surface, the heating due to RF pick up and overheating (see Section 9.6.3)... 

F. A. Gifford, Turbulent Diffusion-Typing Schemes A Review, Nuclear Safety (1976), 17(1) 68. 

The data of figure 2 demonstrate, that at the present choice (3=0,25 in reesterification reaction course only antipersistent (subdiffusive) transport processes are possible (a=l is achieved for low-molecular substances with Df= 0 only), i.e., active time is always smaller than real time. This indicates on the important role of Levy flights in strange diffusion type definition. 

Gifford, F. A. (1976). Turbulent diffusion-typing schemes A review. Sucl. Saf. 17, 68-86. 

There is considerable interest in extending PEFC technology to the direct methanol and formaldehyde electro-oxidation (34, 35). This requires Pt-based bi-metallic catalysts. Tests have been conducted with gas diffusion type Vulcan XC-72/Toray support electrodes with Pt/Sn (0.5 mg/cm, 8% Sn) and Pt/Ru (0.5 mg/cm, 50% Ru). The electrodes have Teflon content of 20% in the catalyst layer. 

Facilitated diffusion within organisms takes place when carriers or proteins residing within membranes—ion channels, for instance—organize the movement of ions from one location to another. This diffusion type is a kinetic, not thermodynamic, effect in which a for the transfer is lowered and the rate of diffusion is accelerated. Facilitated diffusion channels organize ion movements in both directions, and the process can be inhibited both competitively and noncompetitively. It is known that most cells maintain open channels for K+ most of the time and closed channels for other ions. Potassium-ion-dependent enzymes include NaVK+ ATPases (to be discussed in Section 5.4.1), pyruvate kinases, and dioldehydratases (not to be discussed further). 

The three main diffusion types (as opposed to mechanisms) are ... 

Currently, the most frequently used staging system for gastric cancers is the TNM system (Table 1). The Japanese staging system relies on anatomic distribution but the American Joint Committee on Cancer (AJCC) system relies on the number of involved nodes. Traditional prognostic factors for gastric cancer include tumor size and number of involved nodes. It had been suggested that aneuploidy and diffuse-type adenocarci-... 

When flow is turbulent the resulting concentration fluctuations are rapid, numerous, and also small with respect to vessel size. They might be considered to be random, which would lead to a diffusion-type equation. 

As the alternative, a phenomenological description of turbulent mixing gives good results for many situations. An apparent diffusivity is defined so that a diffusion-type equation may be used, and the magnitude of this parameter is then found from experiment. The dispersion models lend themselves to relatively simple mathematical formulations, analogous to the classical methods for heat conduction and diffusion. 

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